Cannon Fuzes

The eighteenth century fuze was a wooden tube several
inches long, with a powder composition tamped into its hole much like
the nineteenth century fuze (fig. 42c). The hole was only a quarter of
an inch in diameter, but the head of the fuze was hollowed out like a
cup, and "mealed" (fine) powder, moistened with "spirits of wine"
(alcohol), was pressed into the hollow to make a larger igniting
surface. To time the fuze, a cannoneer cut the cylinder at the proper
length with his fuze-saw, or drilled a small hole (G) where the fire
could flash out at the right time. Some English fuzes at this period
were also made by drawing two strands of a quickmatch into the hole,
instead of filling it with powder composition. The ends of the match
were crossed into a sort of rosette at the head of the fuze. Paper caps
to protect the powder composition covered the heads of these fuzes and
had to be removed before the shell was put into the gun.

Bombs were not filled with powder very long before
use, and fuzes were not put into the projectiles until the time of
firing. To force the fuze into the hole of the shell, the cannoneer
covered the fuze head with tow, put a fuze-setter on it, and hammered
the setter with a mallet, "drifting" the fuze until the head stuck out
of the shell only 2/10 of an inch. If the fuze had to be withdrawn,
there was a fuze extractor for the job. This tool gripped the fuze head
tightly, and turning a screw slowly pulled out the fuze.

The conical paper-case fuze (fig. 42d), inserted in a
metal or wooden plug that fitted the fuze hole, contained composition
whose rate of burning was shown by the color of the paper. A black fuze
burned an inch every 2 seconds. Red burned 3 seconds, green 4, and
yellow 5 seconds per inch. Paper fuzes were 2 inches long, and could be
cut shorter if necessary. Since firing a shell from a 24-pounder to
burst at 2,000 yards meant a time flight of 6 seconds, a red fuze would
serve without cutting, or a green fuze could be cut to 1-1/2 inches.
Sea-coast fuzes of similar type were used in the 15-inch Rodmans until
these big smoothbores were finally discarded sometime after 1900.

The Bormann fuze (fig. 42a), the quickest of the
oldtimers to set, was used for many years by the U.S. Field Artillery in
spherical shell and shrapnel. Its pewter case, which screwed into the
shell, contained a time ring of powder composition (A). Over this ring
the top of the fuze case was marked in seconds. To set the fuze, the
gunner merely had to cut the case at the proper mark—at four for 4
seconds, three for 3 seconds, and so on—to expose the ring of powder to
the powder blast of the gun. The ring burned until it reached the zero
end and set off the fine powder in the center of the case; the powder
flash then blew out a tin plate in the bottom of the fuze and ignited
the shell charge. Its short burning time (about 6 seconds) made the
Bormann fuze obsolete as field gun ranges increased. The main trouble
with this fuze, however, was that it did not always ignite! !

The percussion fuze was an extremely important
development of the nineteenth century, particularly for the long-range
rifles. The shock of impact caused this fuze to explode the shell at
almost the instant of striking. Percussion fuzes were made in two
general types: the front fuze, for the nose of an elongated projectile;
and the base fuze, at the center of the projectile base. The base fuze
was used with armor-piercing projectiles where it was desirable to have
the shell penetrate the target for some distance before bursting. Both
types were built on the same principles.

A Hotchkiss front percussion fuze (fig. 42e) had a
brass case which screwed into the shell. Inside the case was a plunger
(A) containing a priming charge of powder, topped with a cap of
fulminate. A brass wire at the base of the plunger was a safety device
to keep the cap away from a sharp point at the top of the fuze until the
shell struck the target. When the gun was fired, the shock of discharge
dropped a lead plug (B) from the base of the fuze into the projectile
cavity, permitting the plunger to drop to the bottom of the fuze and
rest there, held by the spread wire, while the shell was in flight. Upon
impact, the plunger was thrown forward, the cap struck the point and
ignited the priming charge, which in turn fired the bursting charge of
the shell.